1. Field of the Invention
This invention relates to ski structures and particularly to a ski structure having greater torsional strength coupled with sufficient longitudinal flexibility to provide good directional control.
2. The Prior Art
Many forms of ski construction have been devised using what amounts to an external boxlike structure filled with a material different from the outer parts. A typical material used in the outer boxlike structure is fiberglass or, more broadly, fiber-reinforced plastic (FRP). Among the materials that have been used in the internal part of the ski structure have been layers of wood, spaced ribs with air between them, and expanded plastic material that is also referred to as foamed material. Some of the internal structures of skis have incorporated what is known as a torsion box extending longitudinally along the central part of the ski. The torsion box is intended to improve the twisting characteristics of the ski. In some cases the torsion box has been filled with foamed material, while in other cases it has simply been left open. Another internal structure in some skis has been referred to as an omega structure because it consists of ribs or plates joined together so that two of them rest on the bottom surface of the boxlike structure and two others extend at an angle toward a top rib that joins the angularly disposed ribs just under the top part of the boxlike structure. The angularly disposed members are supposed to absorb angularly directed forces such as are encountered in making sharp turns.
The disadvantage of ski structures of the type described in the preceding paragraph is that the torsion boxes as made heretofore have not been sufficiently resistent to laterally directed forces, and the omega structures have been subject to separation of the ribs from each other and from the top and bottom parts of the boxlike structure due to excessive lateral forces.